Exercise-induced pulmonary hemorrhage (EIPH) is a condition common to a large percentage of racing and maximally exercised animals, particularly horses, and is defined by the appearance of blood in the lungs of the animal following a strenuous exercise routine.
A smaller percentage of these animals are commonly designated "bleeders" aptly describing the appearance of blood in the nostrils of the animal. This condition appears to be only symptomatic of the underlying source of the bleeding which originates as hemorrhaging in the lungs of the animal.
As current techniques have permitted, for example, with the use of fiber-optic endoscopes, veterinarians have determined that the source of the blood in the nostrils of the animal originates, for the most part, in the lungs of the animal and not from the nostrils as was previously thought.
Mills U.S. Pat. No. 5,132,118 elucidates much of the current theory, techniques and compositions used in the determination and treatment of EIPH.
The Mills patent describes the major lesions of EIPH as multiple, separate and coalescing foci of moderately proliferative small airway disease accompanied by intense neo-vascularization of the bronchial circulation. These lesions are bilaterally symmetrical and confined to the dorsal angle of the lungs. Lesion extension occurs only along the dorsum of the lungs. Microscopic examination of the lungs of horses dying of EIPH has revealed engorgement of the pulmonary arteries, veins and capillaries and rupture of the capillaries with hemorrhage into alveoli, bronchioles, bronchi, interstitium and subpleural tissue. The severity of engorgement and hemorrhage varied from almost nonexistent to massive in various areas of the lung, but the caudal portion of the lung lobes was the site of the most severe hemorrhage. Focally extensive pleural and interstitium fibrosis, and bronchiolitis were often accompanied by severe hemorrhage around large vessels and airways. Hemosiderophages also were present within this fibrous tissue, particularly at the junction of the pulmonary parenchyma and the deep layers of the pleura.
Numerous procedures have been performed in an attempt to prevent EIPH such as change in food, bedding or ventilation, application of external cold compresses to the nasal turbinate area, intermediate application of cold water over the thorax, and tying up the tail.
More recently, various parenteral agents have been utilized in an effort to diminish the magnitude of EIPH in racing or near maximally exercising horses, namely furosemide, atropine, estrogens, coagulants, clenbuterol, (VENTIPULMIN.TM.), ipratroprium (ATROVENT.TM.), cromolyn (INTAL.TM.), intravenous saline infusion and steam inhalation. Hesperidin-citrus bioflavanoids administered orally do not alter the prevalence of the pulmonary hemorrhage. Enforced rest, with a convalescence length much longer than three months duration, does not change the repeatability of the EIPH episodes which recur upon resumption of training and upon attaining maximal exercise form.
The hereinbefore referenced U.S. Pat. No. 5,132,118 is directed to the prevention or treatment of EIPH in a equine specimen by administering a mixture of urea, alkaline potassium salts and optionally magnesium salts. Neither the use of ACE inhibitors nor the theory required to contemplate the use of such compounds in the prevention or treatment of EIPH is recognized in this patent.
Other patents which disclose various treatments for EIPH include Blackmer et al. U.S. Pat. Nos. 4,722,334 and 4,955,372. These patents are directed to the administration, via inhalation, of a humidified gas stream as a treatment for horses including a treatment for EIPH. These patents also do not contemplate ACE inhibitors in treatments for EIPH.